Q&A: Toe Amputation

Abstract

QUESTION: Using the AMA Guides, Fifth Edition, how do I rate a laceration to the left foot that resulted in amputation of the third toe at the middle of the proximal phalanx along with some numbness to the next toe?ANSWER: In the AMA Guides, Fifth Edition, Chapter 17, The Lower Extremities, provides less detail on the assessment of amputation of phalanges than does Chapter 16, The Upper Extremities. However, the criteria listed in Chapter 17 and principles from Chapter 16 can be used to define impairment.Table 17-32, Impairment Estimates for Amputation (5th ed, 545) provides the following information:The first number is the whole person impairment, the second number in parentheses is the lower extremity impairment, and the third number in square parentheses is the foot impairment.If more than one toe is involved, by analogy to the Chapter 16 (page 443), the foot impairments for amputation of each involved toe are added at the foot level, converted to the lower extremity, and ultimately converted to the whole person.Different values are used for the great toe if amputation is at the MTP joint (17% foot impairment) or the interphalangeal (IP) joint (7% foot impairment). However, this degree of detail is not provided for the lesser toes.The great toe has a role in balance and gait (push off), and the lesser toes have little or no functional role in gait. The middle phalanx of toes 2–5 is very small, and the best analogy to an amputation through the IP of the great toe would be amputation through the proximal interphalangeal (PIP) joint of a lesser toe.With the great toe, the difference in amputation at the IP joint vs the MTP joint is 41% (7 foot/17 foot). The value halfway between the MTP joint and IP joint is 12% foot (midpoint between 7 and 17), this being 70% (12/17) of the value assigned to amputation at the MTP joint. Therefore, it would be reasonable to conclude that amputation at the PIP joint of the lesser toes would be 1% foot (41% of 3% foot). Amputation half way between the MTP and IP joint would still be 1% foot impairment. It would be reasonable to assign “3rd toe amputation at middle of proximal pha-lange” as 1% foot.It is difficult to quantify what the impairment would be for “some numbness to the next toe” after laceration. In assessing impairment of upper extremity digits, total sensory loss is assigned a value of 50% of the amputation value and partial sensory loss is assigned 25%, as noted in Table 16-5, Sensory Quality Impairment Classification (5th ed, 447). Partial sensory loss in the upper limb is loss associated with a known nerve injury and decreased sensation on physical exam. Partial sensory loss does not mean that “it feels odd when you touch me there,” but rather it is the inability to recognize touch (either monofilament stimuli not perceived at all or decreased 2 point discrimination). Therefore, using the description of “some numbness” and assuming an abnormal sensory exam, but no total anesthesia, it would be reasonable to assign a value of 25% of the amputation value. If one used the value at the MTP joint, this would be 1% (25% × 3% foot).The values of 1% foot for the amputation and 1% foot for sensory disturbance are combined, resulting in 2% foot impairment. This is converted to lower extremity by multiplying by 0.7, resulting in 1% lower extremity, which is equivalent to 0% whole person per Table 17-3 (5th ed, 527).If you had assigned the entire amputation value for the lesser toe, for example, 3% foot, and for the toe with sensory disturbance at 1.5% foot (50% of the 3% foot value for amputation), you would have 4.5% foot. This converts to 3% lower extremity, which is also equivalent to 1% whole person.You did not state the residual motion in the MTP joint of the third toe or of the adjacent lacerated toe. If MTP joint motion is abnormal, there may be additional impairment from Table 17-14 (page 537) of loss of motion or additional impairment for ankylosis from Table 17-30 (page 543).